PEMS: From vehicle emission measurement to emissions modelling. EMISIA WORKSHOP, Zurich,

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1 PEMS: From vehicle emission measurement to emissions modelling EMISIA WORKSHOP, Zurich,

2 Background PEMS measurements are currently required by legislation for vehicle type approval For research purposes, PEMS offer a unique source of emission information that can be used for Technology assessment Emission factor development Input to air quality modelling Data handling, processing and QA/QC can be overwhelming We can help in all stages of PEMS measurement and data handling Following slides show tools and methods developed by Emisia and implemented by the Environmental Protection Department of Hong Kong 2

3 PEMS systems available by EMISIA AVL M.O.V.E GAS PEMS is AVL M.O.V.E PN PEMS is OBS-ONE GS PN HDV Type + NO, NO2 : UV CO, CO2: NDIR O 2: Elec-Chemical P: 220 W, 2 h on batteries PN: Diffusion Charger CO, CO 2 : NO, NOx: Dual CLD THC: FID PN: CPC P: 450 W, 4 h on batteries

4 Extensive experience with Light Duty Vehicles testing Trip Start/End 36m 538m Altitude 36m PEMS equipment consists of several units installed on the vehicle: Gas analyzer connected with heated line to tailpipe OBD (CAN) data reader device GPS unit Several ambient condition sensors Exhaust gas temperature Exhaust flowmeter pending System control unit, which ensures simultaneous recording for all signals

5 Technical Advisors to Hong Kong PEMS testing of buses

6 Why PEMS measurements can become a headache Instrument diversity (various PEMS devices, exhaust flowmeter, GPS, barometer, speedometer, OBD reader ) Format, syncing, Data volume Single 1-h trip easily creates 20Mb of data Processing methods Regulatory or other methods to come up with g/s or g/km data 6

7 PEMS data handling PEMS data handling & IT infrastructure Data analysis Emission Modelling Collection and Organization Storage and Indexing IT interface (web, other) System Update & Maintenance Grouping Corrections Processing (regulatory or other) Analysis Assessment New emission model development (various scales) Enhancing existing models (e.g. COPERT, etc.) 7

8 PEMS data flow Raw data file server PEMS Measurement Output files Processed data storage Visualisation Emission factors Statistics 8

9 9 QA/QC procedures

10 Time Alignment The user can opt to find the optimal time shift automatically (e.g. correlation) or enter an offset manually The charts are fully interactive the target series can be dragged to all directions and zoomed in/out. 10

11 Examples of PEMS data calculation algorithms Gaseous data PM data 11

12 IT infrastructure Log tables Processed Grouping entity TIME SEQUENCE Sec-by-sec entities General and lookup tables Grouping entity (VEHICLE TEST) Header table Header table Header table (Zero/Span) Processed data table - main Processed data table - secondary Processed data table QA/QC Raw data table Raw data table (Zero/Span) Time-independent entities Standardized Raw data table Standardized Raw data table (Zero/ Span) Header table Processed data table - main Processed data table - secondary Processed data table - QA/QC 12

13 CO 2 rate and exhaust temperature Example of graph Snapshots of emission performance by combining different signals 13

14 NOx as a function of Euro standard Example of emission factor 500-m integrations of emission rates as a function of mean speed 14

15 CO 2 emissions variability per speed class Example of statistics Distribution of 1 Hz CO 2 emission rate as a function of speed class. Box-plots and outliers shown 15

16 Environmental Assessment of LPG Taxi Fleet 18 LPG taxis 370 hours of field data Euro 2 to Euro 5 technology Impact of TWC and lambda sensor replacement Time- and distance- integration Vehicle speed and road slope impact on emission levels 16

17 SCR and DPF diesel bus retrofits 6 double-deck diesel buses DPF and SCR; SCRT retrofit 17 Emission levels Effect of DPF technology Impact of SCR on criteria pollutants Impact of operation conditions

18 Assessment of urban hybrid buses performance 6 Euro V diesel and 6 Euro VI hybriddiesel double-deck buses SCR (all); DPF and SCR (hybrids) 18 FC benefits of hybrids Benefits of combining hybrid and Euro VI technologies Distance-based and energy-based EFs Effects of driving, ambient, operational conditions on EF and FC

19 Emissions modelling based on PEMS data Meso-scale emission modelling Micro-scale emission modelling Velocity-power plot and power histogram Scatterplot Matrix for HC Emission Rate with Positive VSP Basis Functions 19 NOx emissions measurement compared to simulation

20 Regulatory evaluation and visualization Moving Average Window (MAW) interface (EMROAD method) Checks compliance criteria Produces CO 2 MAW chart Vehicle Specific Power (VSP) interface (power binning method) Input: rolling resistance, vehicle mass, the road gradient Produces a chart of the VSP bins for three speed classes 20